General Questions

1. Is the rhythm fast or slow?

One of the most important questions in your decision tree relates to the rate of the rhythm. Calculating the rates is easy (for a refresher, see Chapter 3, Paper, Tools, and Calculating Rates). For our purposes, we need to know that all rhythms will always fit in one of three categories based on the rate:

1. Slow. The rate is considered slow if it is less than 60 beats per minute (BPM). Rhythms with rates this slow are usually referred to as bradycardias.
2. Normal. The rate is considered normal if it between 60 and 99.
3. Fast. The rate is considered fast if it is greater than 100 BPM (> 100 BPM).

2. Is the rhythm regular or irregular? If irregular, is it regularly irregular or irregularly irregular?

Do the P waves and QRS complexes follow a regular pattern with the same intervals separating them, or are the intervals different between some or all of the beats? This is a great tool to help you narrow down the rhythm, as you will see in the upcoming pages.

There is an additional question you must answer if the rhythm is irregular: Is it regularly irregular or irregularly irregular? At first glance, this statement can be confusing. A rhythm is regularly irregular if it has some form or regularity to the pattern of the irregular complex. An example would be a rhythm in which every third complex comes sooner than the preceding two. Therefore, the intervals would be long-long-short, long-long-short, in a repeating pattern that is predictable and recurring in its irregularity.

An irregularly irregular rhythm has no pattern at all. All of the intervals are haphazard and do not repeat, with an occasional, accidental exception. Luckily, there are only three irregularly irregular rhythms: atrial fibrillation, wandering atrial pacemaker, and multifocal atrial tachycardia. You should commit this differential diagnosis to memory, as it will get you out of some tight spots.